If you no longer want to receive invites from someone, you can mute them. Once muted, you won’t get any activity invites from them anymore.
Exception: If the person creates a "by invitation only" activity, you can still request to come.
Muting affects:
Push notifications
Email notifications
The For you section under Invitations
Private messages:
The muted person can still send you private messages, but you will not receive any push or email notifications about them.
How to mute someone:
Go to their profile, tap More and then Mute user. The user will not be informed about this.
To unmute:
Go to Profile and then Muted Members to undo the mute at any time.